Conversations with Albert Einstein

Conversations with Albert Einstein

R. S. Shan kl and
Case Institute of Technology, Cleveland 6, Ohio
(Received 11 September 1962)

The following account of talks with Professor Einstein are the notes made by the writer in
Princeton immediately after each of five visits about ten years ago. They were originally
written without any thought of publication, but rather as a private record of very wonderful
experiences. However, since they may contain matters of interest to others, it has been decided
to publish them.

IT was my privilege to call on Professor Ein-
stein in Princeton on five occasions in the
period 1950-1954. The conversations at these
visits dealt principally with the work of Albert
A. Michelson at Case, the Michelson-Morley
experiment and the studies which led to clarifi-
cation of the results obtained by Dayton C.
Miller at Mount Wilson. These conversations
with Einstein were a rare and inspirational
experience, and it has been suggested that they
might be reported so that younger physicists who
have not met Professor Einstein personally might
get a better impression of the kind of man he was.
The notes are exactly as written down at the time
except for minor changes. Consequently, the
reader will find certain repetitions, and perhaps a
few discrepancies. These, however, only em-
phasize the fact that all Professor Einstein's
comments were made from memory, often on
events that had occurred 50 years before our
meetings. Some references and footnotes have
been added for clarification.

I. 4 February 1950

The first visit to Princeton to meet Professor
Einstein was made primarily to learn from him
what he really felt about the Michelson-Morley
experiment, and to what degree it had influenced
him in his development of the Special Theory of

Relativity. I had not had experience in making
appointments with such great men as Einstein,
and I puzzled a good deal about how this should
be done. Finally after considerable hesitation, I
wrote directly to him stating the purpose of my
visit and suggesting a day at the end of the New
York meetings of the American Physical Society
to call on him. I received an immediate reply
from Miss Helen Dukas, Einstein's secretary,
giving me a most friendly invitation to come to
Einstein's office at the fnstitute for Advanced
Study at 11 :00 a.m. on the suggested day.

Needless to say, I was there in more than
ample time and at last I could see him approach-
ing on foot as was his custom. Exactly at 11 :00
a.m. Professor Einstein finished his brisk walk
from his home on Mercer St. to the Institute for
Advanced Study, and after pausing to pick up
his mail, he greeted me, shook hands and invited
me into his office which was room 115. He was
very friendly, informal, and courteous, instantly
impressing one by his marvelous eyes — large,
discerning, but above all, kindly. After first nod-
ding me to a chair, he seated himself at his desk.
His large office was attractively furnished but
was completely devoid of gadgets, honors or
mementos, although his desk was covered with
papers, books and journals. It had an atmosphere
of friendliness and scholarliness.

R . S . SHAKKLAND

48

He began by asking me to remind him of the
purpose of my visit and smiled with genuine
interest when I told him that I wished to discuss
the Michelson-Morley experiment performed at
Cleveland in 1887. When I reminded him that
Michelson had been Professor of Physics at Case
for eight years, he nodded. I showed him the
drawing of the apparatus as reproduced in my
paper. 1 He seemed greatly interested, asking me
to sketch on his blackboard the details of their
method of floating the stone on mercury. I was a
little hesitant, because the blackboard was
covered with neat equations dealing with his new
Unified Field Theory. But he waved his pipe and
said, "Oh rub that out!" I made some sketches,
and he commented on them with keen interest.
He was especially pleased with the float design
that required the use of so little mercury. His
eyes brightened, and he chuckled at this. He
asked me where the parts of the apparatus are
now located, especially the stone, and when I
told him it had disappeared, he said, "It would
be nice if all the parts could be brought together
again."

When I asked him how he had learned of the
Michelson-Morley experiment, he told me that
he had become aware of it through the writings
of H. A. Lorentz, 2 but only after 1905 had it come
to his attention! "Otherwise," he said, "I would
have mentioned it in my paper." 8 Pie continued

iR. S. Shankknd, Am. J. Phys. 17, 487(1949).

2 H. A. Lorentz, Arch. Need. 2, 168 (1887), and many
letter references.

3 A. Einstein, Ann. Physik 17, 891 (1905) ; also in English
translation (Dover Publications, New York). My col-
league, Professor L. L. Foldy makes the following com-
ment: Although Einstein may have been unaware of the
Michelson-Morley experiment in 1905, he does make
reference in the second paragraph of his 1905 paper to
"unsuccessful attempts to discover any motion of the earth
relatively to the 'light medium'." It is not clear whether
Einstein is here referring to v/c or {v/c} 2 experiments,
particularly since in the next sentence he goes on to say
"They suggest rather that, as has already been shown to
the first order of small quantities, the same laws of electro-
dynamics and optics will be valid for all frames of reference
for which the equations of mechanics hold good." There is
an implication, but by no means a certainty, that the first
reference is to second-order experiments such as the
Michelson-Morley experiment, and suggests the possibility
that Einstein was aware of the negative results of such
experiments if not with the experiments themselves.
Einstein derives the Lorentz-Fitzgerald Contraction but
says nothing about whether there is experimental confirma-
tion. The whole paper is rather strange in the respect that
Einstein reveals very little about what he knows to be
experimentally verified and in that he makes no specific
references to the work of others. The paper in fact presents
an enigma in that it is very difficult to see how much of the

to say the experimental results which had in-
fluenced him most were the observations on
stellar aberration 4 and Fizeau's measurements 5
on the speed of light in moving water. "They
were enough," he said. I reminded him that
Michelson and Morley 6 had made a very accurate
determination at Case in 1886 of the Fresnel
dragging coefficient with greatly improved tech-
niques and showed him their values as given in
my paper. To this he nodded agreement, but
when I added that it seemed to me that Fizeau s
original result was only qualitative, he shook his
pipe and smiled, "Oh it was better than that!"
He thought Zeeman's 7 later precise repetition of
this experiment was very beautiful. He seemed
really delighted when I mentioned to him how
elegant I had found (as a student) his method of
obtaining the Fresnel dragging coefficient from
his composition of velocities law of special
relativity.

I asked Professor Einstein how long he had
worked on the Special Theory of Relativity
before 1905. He told me that he had started at
age 16 and worked for ten years ; first as a student
when, of course, he could only spend part-time on
it, but the problem was always with him. He
abandoned many fruitless attempts, "until at
last it came to me that time was suspect!" Only
then, after all his earlier efforts to obtain a theory
consistent with the experimental facts had failed,
was the development of the Special Theory of
Relativity possible.

This led him to comment at some length on the
nature of mental processes in that they do not
seem at all to move step by step to a solution,
and he emphasized how devious a route our
minds take through a problem. "It is only at the
last that order seems at all possible in a problem."

I showed him what I had written in the paper
about the Michelson-Morley experiment and the

special theory of relativity is a pure mental construct and
how much is an inference from experimental results (or a
theoretical formulation of them) of which Einstein had
knowledge. See also G. Holton, Am. J. Phys. 28, 627
(1960).

4 J. Bradley, Phil. Trans. Roy. Soc. (London) 35, 637
(1728); G. B. Airy, Proc. Roy. Soc. (London) 20, 35
(1871); 21, 121 (1873).

6 H. L. Fizeau, Compt. rend. 33, 349 (1851) ; Ann. Chem.
Phys. 57, 385 (1859).

6 A. A. Michelson and E. W. Morley, Am. J. Sci. 31, 377
(1886).

' P. Zeeman, Proc. Amsterdam Acad. 17, 445 (1914) : 18,
398 (1915).

CONVERSATIONS WITH EINSTEIN 49

Special Theory of Relativity. This he read
eagerly, puffed at his pipe, and nodded approval.
When I suggested that the notice given to
Fitzgerald's contribution was perhaps a little
overemphasized, he said, "Oh no, he had the idea
to try to clear up the mess."

Einstein first met Michelson in Pasadena and
considered him "a great genius — he will always
be thought so in this field." Einstein added that
it was very remarkable that Michelson with
little mathematics or theoretical training and
without the advice of theoretical colleagues 8
could devise the Michelson-Morley experiment.
Michelson 's instinctive feeling for the essentials
of a crucial experiment without completely
understanding the related theories, Einstein con-
sidered the surest sign of his genius. This he feels
was in large measure due to Michelson 's artistic
sense and approach to science, especially his
feeling for symmetry and form. Einstein smiled
with pleasure as he recalled Michelson's artistic
nature — here there was a kindred bond. The
artist was greatly in evidence in the Michelson-
Morley experiment. Einstein remarked, "Most
people would think the experiment silly." 9 I
remarked on Michelson's excellent eyesight and
the great advantage this gave him in optical
experiments. Einstein's eyes lit up and he said,
"Oh, but behind the eyes was his great brain!"

I mentioned the experiments which had dis-
proved the Ritz emission theory of light 10 especi-
ally de Sitter's work on spectroscopic binaries 11
and the null result obtained by D. C. Miller 12 at

8 This is in general true, but the indirect influence of
James Clerk Maxwell was probably decisive in directing
Michelson's interests away from the speed of light meas-
urements to the other problem. While at the Nautical
Almanac Office in 1879 Michelson was able to study a letter
from Maxwell to David Peck Todd [see Nature 21, 314
(1880) ; Proc. Roy. Soc. (London) A30, 109 (1880)] which
discussed basic matters on the possibility of detecting the
earth's motion through space by optical observations.
Professor Todd's reply to Maxwell dated May 19, 1879, has
recently been made available to the writer through the
courtesy of his daughter, Mrs. Millicent Todd Bingham, of
Washington, D. C.

9 Just as my father, F. N. Shankland; my uncle, S. D.
Shankland; and Mr. S. S. Wilson told me that in their
student days at Western Reserve University the Michel-
son-Morley experiment was referred to as though it had
been a failure, since it gave a null result.

10 W. Ritz, Ann. Chem. Phys. 13, 145 (1908).

»W. C. de Sitter, Proc. Amsterdam Acad. IS, 1297
(1913); 16, 395 (1913).

u D. C. Miller, Proc. Natl. Acad. Sci. U. S. 11, 311
(1925).

Case with the modification of the Michelson-
Morley experiment using sunlight. He said he
knew de Sitter well but told me he considered the
most decisive experiment along these lines to be
the repetition of the Michelson-Morley experi-
ment performed with starlight at Heidelberg by
a student of Lenard's (Tomaschek) 13 ; because
here, the high radial velocities involved made the
null results really decisive in establishing the
speed of light to be independent of the motion of
the source. Here we have the true measure of
Einstein the man. Lenard, who along with
Stark, was the most violently Nazi of all German
scientists was referred to by Einstein with com-
plete fairness and with not the slightest trace of
malice or bitterness.

This led him to a discussion of emission theo-
ries of light, and he told me that he had thought
of, and abandoned the (Ritz) emission theory
before 1905. He gave up this approach because he
could think of no form of differential equation
which could have solutions representing waves
whose velocity depended on the motion of the
source. In this case, the emission theory would
lead to phase relations such that the propagated
light would be all badly "mixed up" and might
even "back up on itself." He asked me, "Do you
understand that?" I said no and he carefully
repeated it all. When he came again to the
"mixed up" part he waved his hands before his
face and laughed, an open hearty laugh at the
idea!

Then he continued, "The theoretical possi-
bilities in a given case are relatively few and
relatively simple, and among them the choice
can often be made by quite general arguments.
Considering these tells us what is possible but
does not tell us what reality is."

When I suggested that 'Ritz's theory was the
best of the several emission theories of light, he
shook his head and replied that Ritz's theory is
very bad in spots. 14 But he quickly added, "Ritz
made a great contribution when he showed that
frequency differences are the crucial thing in
spectral series."

I then asked Professor Einstein if he had con-
sidered Michelson and Gale's interferometer

13 R. Tomaschek, Ann. Physik 73, 105 (1924).

14 A. Einstein, Physik Z. 10, 185 (1909).

50

R . S . SHAN'KLAND

measurement 16 of the earth's rotation important.
He said, "Oh, yes, that is Sagnac's experiment 16
with a small velocity and a large area." He
thought the Michelson-Gale experiment very
beautiful but added that "there had existed no
theoretical doubt" as to its outcome.

This was followed by some brief comments on
the new unified field theory. He said that some-
how it must also be made to include "atomicity."
When I asked if he had any experiments in mind
relating to the new theory he said, "No, all
advances must now wait on great developments
in mathematics." The solutions of the nonlinear
partial differential equations of the theory must
be exact to be useful, and any solution obtained
by approximation methods, such as perturbation
theory, would not be helpful. He felt that only
when such rigorous solutions were obtained
would it be possible to see how "atomistic"
phenomena will fit into the unified field picture
and that until this is done, the situation will
continue to be very unsatisfactory.

Here, Einstein made some general observations
about atomic theory and quantum mechanics and
said at the outset, "You know I am in disagree-
ment with most of my colleagues on the quantum
theory." He felt that they were not "facing the
facts" in their present methods. In fact, he spoke
much more strongly than this and several times
said that they had "abandoned reason" and that
quantum-mechanical physics "avoids reality and
reason." He spoke several times of Bohr whom he
greatly likes and admires but with whom he dis-
agrees in many fundamental ways. He said that
Bohr's thinking was very clear but that "when
he begins to write he becomes very obscure and
that "he thinks of himself as a prophet." Here I
had difficulty in deciding whether Einstein was a
bit stubborn or whether he was really convinced

16 A. A. Michelson and H. G. Gale, Astrophys. J. 61, 137,
140 (1925). Nature 115, 566 (1925). In this experiment,
two beams of light were made to travel in opposite direc-
tions in a partially evacuated pipe which enclosed a large
area — at that time a field — now built up as the Clearing
Industrial Area near the Chicago O'Hare airport. The
earth's rotation affected the times of travel of the two light
beams by amounts consistent with the predictions of both
the special and general theories of relativity, and also the
older aether theory.

16 G. Sagnac, Compt. rend. 157, 708 (1910); J. phys. 4,
177 (1914). In this experiment, two beams of light travelled
in opposite directions in an optical system rotated at high
speed in the laboratory. Sagnac's measurements preceeded
the general theory of relativity.

that quantum mechanics must change its view-
point in a very fundamental way to make further
progress possible.

Our conversation then returned to the Michel-
son-Morley experiment and the Special Theory
of Relativity, f could not help feeling that this
elegant special theory, the product of his youth-
ful efforts, held the place nearest to his heart. 1
asked him if he felt that writing out the history
of the Michelson-Morley experiment would be
worthwhile. He said, "Yes, by all means, but you
must write it as Mach wrote his Science of
Mechanics." Then he gave me his ideas on
historical writing of science. "Nearly all his-
torians of science are philologists and do not
comprehend what physicists were aiming at, how
they thought and wrestled with their problems.
Even most of the work on Galileo is poorly done."
A means of writing must be found which con-
veys the thought processes that lead to dis-
coveries. Physicists have been of little help in
this because most of them have no "historical
sense." Mach's Science of Mechanics, however, he
considered one of the truly great books and a
model for scientific historical writing. He said,
"Mach did not know the real facts of how the
early workers considered their problems," but
Einstein felt that Mach had sufficient insight so
that what he says is very likely correct anyway.
The struggle with their problems, their trying
everything to find a solution which came at last
often by very indirect means, is the correct
picture. He also expressed the highest regard for
Laue's scientific writings.

I referred to Einstein's visit to D. C. Miller at

Case in 1921 ; an event which I am sure was

decisive in Miller's work on the aether-drift

experiments from 1921 through 1926. He told me

that when he came to the United States that

year, he did not know a word of English. On the

trip he picked up some by ear, He told me, "I am

the acoustic type ; I learn by ear and give by

word. When I read I hear the words. Writing is

difficult, and I communicate this way very

badly." He added that he never really felt sure of

the spelling of any English word. He told me that

he even hated to write his Autobiographical Notes

in German. 17

17 Paul Arthur, Schilpp, Albert Einstein, Philosopher-
Scientist (Library of Living Philosophers, Evanston, Illi-
nois, 1949).

CONVERSATIONS WITH EINSTEIN

51

My lasting memory of Professor Einstein will
be of his kindness and courtesy, his deep respect
for the work and personalities of others. There
was in his manner not the slightest condescension
but rather an earnest desire that all my questions
be answered and that his own views or position
be clearly stated. He told me how the day before
he had tried "to explain simultaneity to a lay-
man." He said, "It is very hard sometimes to
explain these things you know." Finally, when
all my questions were answered, we both rose and
he walked slowly to the door with me. On leaving
I again shook his hand and said, "Thank you
sir." He smiled again and the great deep eyes lit
up as he replied, "Thank you!"

II. 17 November 1950

Up early and to the Pennsylvania Railroad
Station for breakfast before taking the train for
Princeton where I arrived at 9:20 a.m. It was a
beautiful day, and I walked first to the Nassau
Tavern and called the Institute for Advanced
Study where the mathematics secretary arranged
for me to see Einstein at 11 :00 a.m. I walked to
the Institute and after chatting with the secre-
tary spent an enjoyable hour in the library and
lounge. About eleven o'clock I started toward
Einstein's office. He had arrived promptly at
that hour, and when the secretary told him I was
in the lounge, he started off full-tilt to get me! It
was all the secretary could do to catch him and
bring him back to his office door where I was
waiting. He invited me in and after we were both
seated, asked me about my visit. When I told
him I wanted to tell him some of the things we
had found in D. C. Miller's observations 18 he
said, "Do you really think there is something in
them?" When I replied that I felt confident that
a thorough analysis of the observations might
show that they were consistent with a null re-
sult, he was all interest and excitement. We both
got up and went to the blackboard and for an
hour worked there, walked around the room
while talking, sat on the table, and had a wonder-
ful time. He was far more animated than on my
visit in February. Several times he exclaimed to
me, "This is very beautiful!" I told him that it
had always been a great puzzle to me why

18 D. C. Miller, Revs. Modern Phys. 5, 203 (1933), and
original data sheets given by Miller to the writer.

Miller's data seemed to yield this small positive
result and that I had concluded that it might be
due to his method of treating the data. On the
blackboard I carried through a "sample run" in
outline and explained my view that connecting
the 16 averaged points by line segments was
wrong. He emphatically agreed and added that
what this really does to the data would require
"a very complicated analysis." Then I told him
of the Wood's Hole work on ocean wave analysis
showing that mechanical analyses such as those
given by Miller's Henrici Harmonic analyser
might introduce false periods in finite sets of
data. 19

I outlined our plan to apply an auto-correlation
analysis to Miller's data, and told him about the
machine R. L. Stearns was building to carry out
the analysis. He did not know of this method but
immediately understood when I explained the
process and he pointed out that it would not give
phases and that these are more important for an
"aether-drift" than amplitudes. This I agreed to
but also replied that if the data seemed to give a
null result in amplitude by this method of analy-
sis, then the phases would not be a consideration.
He repeated several times during our talk that
since the phases found by Miller ("which fix the
direction in space") were not consistent, this was
the strongest argument against the drift reported
by Miller. He said several times, however, that
he (and also H. A. Lorentz) considered Miller an
excellent experimenter and thought his data
must be good. He emphasized that mere multi-
plication of data is not a good thing. This re-
inforced our resolve to concentrate on that part
of Miller's data where he indicated "excellent
conditions." Einstein also told me that H. A.
Lorentz had studied Miller's work for many
years and could not find the trouble.

Einstein asked about strains in the interfer-
ometer and the experimental conditions at
Mount Wilson. He emphasized that if there is a
systematic effect, however small, it must be

19 Note added February 1955 : It was not until early 1954
after the complete analysis of variance results were avail-
able that we were convinced that the periodic effects found
by D. C. Miller were not due to statistical fluctuations or
to his method of analysis. Only then did we plunge deeply
into a study of the temperature effects to find the real cause
of Miller's results (see reference 34). The essential correct-
ness of Miller's harmonic analysis had meanwhile been
proved by the autocorrelation analysis carried out by R. L.
Stearns, M. S. Thesis, Case Institute of Technology (1952).

R . S . SHANKLA.N D

52

explained. He was most interested and encour-
aged me to carry the problem through.

I then told Professor Einstein about the un-
published 1924 Case data, and he was very
interested. He fully understood why Miller did
not consider the null results of this work signifi-
cant because it was done in a basement room
where the "drag" would be large. He pointed out,
however, that there should be nearly as much
"drag" at Mount Wilson as in the Case basement
room due to the mass of the interferometer
itself. He also reminded me that any "drag"
would be inconsistent with aberration. I told him
that I felt the 1924 results should be published
as these seemed to be among the best of all data
taken in these experiments. I also told him of
Miller's observations 18 using sunlight as a source
and that these seemed to me to be better than
Tomaschek's. 13 He did not protest but nodded
agreement. He likes Tomaschek's work with
starlight, however, because of the large radial
velocities.

We discussed the difference between the
Morley-Miller result of 1904 and Miller's 1925-
26 experiments. 18 He said that he had always
been puzzled by the difference between these two
groups of experiments. I suggested to Einstein
that the discrepancy might be due to the method
of analysis. 20 1 showed him at his blackboard that
by reporting the calculated velocity of the earth
"through the aether" (v) as given by his experi-
ments, Miller tended to find a greater average
speed than would be the case if he had averaged
the amplitudes of the fringe displacements (A). 21
Einstein agreed that our study should be con-
fined to the experimental amplitudes and phases
of the actual observed fringe displacements
"until a trend was certainly established."

Several times during our talk, Einstein said,
"This is very nice" and laughed his hearty naive
laugh. Several times also he asked me very
seriously, "Why did not Miller find this?" 22 This
seemed a great puzzle to him, one that I could

20 Note added in June 1962-our later studies (reference
34) make it certain that the differences were in fact due to
the greatly differing temperature conditions existing in the
basement laboratory at Case and at Mount Wilson.

21 This is due to the relationship between the observed
fringe displacements (A) and the calculated speed (v) :
A —2L(v/c) 2 , where L is the optical path length of the
interferometer, and c is the speed of light.

22 Our final conclusions (reference 34) were different !

not resolve, but I did tell him of Miller's great
concentration on sound and the flute in his later
years. He asked me about Miller's acoustical
work, and when I told him of Miller's studies of
vowels and their relation to Helmholtz's theory,
he was much interested. He had not realized that
Helmholtz had done this and exclaimed "What
that man accomplished!" I also told Einstein of
Miller's flute collection and this seemed to inter-
est him a great deal.

Toward the end of our talk, I asked if Michel-
son had ever told him how he came to invent the
interferometer. He said no. I told him that I felt
it had been developed in Paris while he worked
with Jamin and Mascart. He agreed that this was
very probable and that Michelson's basic ideas
for the Potsdam experiment had also evolved in
Paris. He exclaimed at one point, "How many
ideas Michelson originated for optical research!"
Einstein then asked me what I thought about the
supposed variability in the speed of light. 23 I told
him I felt it was not a real effect.

At last I said goodbye after an hour of pleasure
and inspiration with this great man — so kind, so
gentle, so interested only in the truth.

III. 2 February 1952

I left New York on the 9:15 a.m. train and
arrived at Princeton at 10:40. I taxied to the
Institute for Advanced Study where the tele-
phone girl told me that Einstein's secretary had
called to leave word that he was coming over to
see me. "He is expecting you," she said. At 10:55
I saw him walking briskly along the path, from
the direction of Oppenheimer's white house, in
stocking cap, long coat and cigarette. He came
in, spoke to the telephone girl and then came
rapidly down the corridor towards his office
where I stood. He extended his hand and very
cordially invited me into his office (room 115).
He had apparently put his cigarette into his coat
pocket, and as we took off our coats he had a small
conflagration in his. When I thanked him for
coming over to see me he said, "I always come
to the office." He sat down behind his desk and
invited me to be seated. Then in a most friendly
way he asked me, "What is your question?"

I asked him if he had heard of the recent work

23 R. T. Birge, Reports on Progress in Physics (The
Physical Society, London, 1941), Vol. VIII, pp. 100-101.

CONVERSATIONS WITH EINSTEIN

53

of Synge. 24 When he said no, I told him of our
correspondence and gave an account of my
understanding of Synge's theory relating to the
concept of a rigid body in relativity and its
possible bearing on Miller's results in the Michel-
son-Morley experiment. He felt very strongly
that Synge's approach could not be significant
and that the results of any experiments of the
kind proposed by Synge would be irrelevant to
questions regarding relativity, including the
relativistic concept of a rigid body. When I told
him that Synge predicted a small positive effect
due to the acceleration of the interferometer,
Einstein asked, "What acceleration, the rotation
of the instrument?" When I told him that I
understood it was the acceleration due to the
rotation of the earth on its axis through the
possible coupling with the interferometer through
the "pin" (assumed by Synge), he shook his head
vigorously and replied, "This can have no con-
nection. All such accelerations, including any due
to Coriolis forces would be completely indis-
tinguishable from gravity." Einstein stated
strongly that he felt Synge's approach could have
no significance. He felt that even if Synge de-
vised an experiment 25 and found a positive result,
it would be completely irrelevant. He was sure
that all questions relating to the coupling of the
"pin" and rigidity of the apparatus were mean-
ingless in relativity. He emphasized, however,
that the question of "rigidity" was most impor-
tant and needed study. He talked at some length
about the problem of rigidity in relativity,
emphasizing its importance for such questions as
the finite speed of propagation of signals, etc.
However, he told me that no significant definition
or theory of rigidity existed which corresponded
to "reality," since the only rigid bodies yet
studied were either those having zero mass or
whose behavior could be treated in the absence
of all external forces.

He then referred to the fact that I had pre-
viously told him that "Miller's positive result
obtained at Mount Wilson could be explained by
his method of analysis, and he felt sure that this
was a more likely explanation than Synge's. Once

24 J. L. Synge and G. H. F. Gardner, Nature 170, 243
(1952); also Proc. Roy. Dublin Soc. 26, 45 (1952).

25 Such an experiment devised by Ditchburn did in fact
give again a null result for the aether-drift: R. W. Ditch-
burn and O. S. Heavens, Nature 170, 705 (1952).

again he told me that Lorentz could never explain
Miller's result and felt that it could not be ig-
nored, although Einstein was not sure whether
Lorentz really believed Miller's result.

I asked Einstein if Synge was justified in
attacking problems regarding acceleration by
special relativity, and he said, "Oh yes, that is all
rightas long as gravity does notenter ; in all other
cases, special relativity is applicable. Although,
perhaps the general relativity approach might be
better, it is not necessary."

I then asked him about the speech he gave in
Berlin on Michelson's death in 1931 and asked
especially about his reference to the Michelson-
Morley experiment and its relation to general
relativity. He had apparently forgotten the
speech, much less what he had said, so this came
to naught. However, his eyes shone as he thought
about Michelson and once more he referred to
him as "an artist." When I told him that Michel-
son's daughter (Mrs. Dorothy Michelson Stevens)
had told me of Einstein's visit to her parents
home in California, he smiled broadly and seemed
to recall it with great pleasure. He was very
complimentary about the Michelson-Gale ex-
periment but said that at first he did not under-
stand how it worked.

I referred again to Synge's proposed experi-
ment — contrasting the possible difference be-
tween Miller's and Joos' 26 apparatus regarding
"pin" etc., — but he just shook his head. Appar-
ently he had completely forgotten Joos' work.

I next asked Einstein about his early interest
in de Broglie's work. He told me that in his
studies of the degeneracy of gases he had worked
out a theory for the statistical fluctuations from
the entropy which contained "an undulatory
term," which he identified as bearing a close
relationship to de Broglie's ideas on matter
waves. 27

He went on to say that in quantum theory he
was "in the opposition" because he felt that the
^ functions do not represent reality. He described
quantum mechanics as a brilliant "short-cut"
which successfully avoided many of the difficul-
ties and the hard work which the final correct
theory must face and solve. He talked at length

26 G. Joos, Ann. Physilc 7, 385 (1930); Naturwissen-
schaften 38, 784 (1931).

2T A. Einstein, Berliner Berichte, p. 261 (1924); p. 3
(1925).

54

R . S . SHAKKLAND

about the i/< function description especially as
related to a wave-packet localizing an electron to
the extent permitted by the Uncertainty Prin-
ciple. (He did not call it by this name nor did he
mention Heisenberg.) Descriptions of the posi-
tion, velocity, spreading with time of the \p
function, etc., he did not like at all. He empha-
sized that quantum theory only admits defining
the position of a particle exactly by an act of
observation which completely changes it. He
readily admitted, however, that quantum theory
provided the only way at present known for
describing quantum (stationary) states. He felt
that the if/ description was not "reality" and that
the quantum-theory people all have a "narrow
view" (holding his hands to his eyes to show me).
In arguing that the quantum view was not com-
plete, he emphasized that it had no explanation
for the constancy of the elementary electrical
charge. He added, however, that "it is correct to
use quantum theory as long as it is useful, even
though it is not a complete description." He told
me that J. R. Oppenheimer was sure that quan-
tum theory provided a complete solution and
description but added, "I have talked very little
to him about it." Einstein felt sure that the final
correct theory must start with general relativity
(although he said that his own attempts in this
direction were probably wrong).

The difficulties in quantum theory are becom-
ing very acute in nuclear theory which Einstein
considered hopeless in its present state. He felt
that just the multiplication of facts and experi-
mental data in nuclear physics would not clarify
the situation or lead to a final correct theory.
This is in marked contrast to the prevalent view
that experimental facts will utimately reveal
regularities and thus give the hints that will lead
to a theoretical solution. He disagreed com-
pletely with this view and emphasized again that
even in atomic problems the quantum theory
description is unsatisfactory. We talked about
the big machines used in nuclear physics, and he
feared a real danger from these for the scientific
method. They make us "slaves to the means,"
and new ideas would be lost or never found. 28

I asked if he had seen Dirac's article in Nature 29
on the aether, and he said no and asked me about

28 One must remember that this was 10 years ago !
*>P. A. M. Dirac, Nature 168, 906 (1951).

it. 1 told him a little, and when I mentioned the
relationship of the Uncertainty Principle to the
impossibility of denning a unique reference
direction in space, he said, "I do not like it!" He
continued to say that if one needed properties
that are in space before matter, the field equa-
tions, etc., are introduced, then you would need
an aether but that this need does not exist. He
went on to explain why "Maxwell's equations are
not reality," but I did not follow this.

He then recalled Synge and his work and asked
me if he were not somewhat of a philosopher. He
again said that more experiments were not
necessary, and results such as Synge might find
would be "irrelevant." He told me not to do any
experiments of this kind.

As I left Einstein, 1 realized that he seemed
much older. His eyes still had the deep smile but
were not as keen as before. His hands were a
little feeble, and when I asked him if he still
played the violin (a Brahms' score was on his
desk) he said, "No, my fingers don't work any-
more. " I thanked him for his time, but he waved
his hands in protest. Then we shook hands, he
smiled, and I left.

IV. 24 October 1952

It was a beautiful October day, and I walked
down Mercer Street to Professor Einstein's home
which is number 112. Einstein's secretary greeted
me and led me upstairs and to the rear of the
house to Professor Einstein's study. This was an
attractive simple room with open white book-
shelves on two sides filled in rather a disordered
fashion with books, reprints, and papers.
Towards the back of the room large windows look
out on a yard where today the trees are in their
last autumn foliage. I was struck at once by a
fine portrait of Maxwell on the wall and by
another of Faraday. Professor Einstein was
sitting on the adjacent porch when I entered, but
he immediately came into the study and greeted
me in a very friendly way. He asked me to be
seated by his desk, and I then told him of the
plans at Case to celebrate the 100th birthday of
Michelson at which time I was to speak on his
work and especially about the interferometer
experiments. He smiled broadly and expressed
real satisfaction that we were doing this. He said,
"I always think of Michelson as the artist in

CONVERSATIONS WITH EINSTEIN

55

science. His greatest joy seemed to come from the
beauty of the experiment itself and the elegance
of the method employed. He never considered
himself a strict 'professional' in science and in
fact was not — but always the artist."

I asked Professor Einstein where he had first
heard of Michelson and his experiment. He re-
plied, "This is not so easy, I am not sure when I
first heard of the Michelson experiment. I was
not conscious that it had influenced me directly
during the seven years that relativity had been
my life. I guess I just took if for granted that it
was true." However, Einstein said that in the
years 1905-1909, he thought a great deal about
Michelson's result, in his discussions with
Lorentz and others in his thinking abdut general
relativity. He then realized (so he told me) that
he had also been conscious of Michelson's result
before 1905 partly through his reading of the
papers of Lorentz and more because he had
simply assumed this result of Michelson to be
true.

I told Einstein of my father's report as a
student at Western Reserve University that the
Michelson-Morley experiment was considered to
have been a failure and that Morley was in a
certain sense an object of pity. He shook his head
vigorously at this and said, "No one should have
said that! Many negative results are not highly
important, but the Michelson experiment gave a
truly great result which everyone should under-
stand."

Professor Einstein felt that the work of
Lorentz should be studied much more by present-
day physicists. He said that the Maxwell electro-
magnetic theory had not been left in good form
and really only applied to a vacuum. This was
made clear by the work of Lorentz who showed
that electric field and displacement must always
be related by the properties of the medium, and
so theory must assume or find these properties
before it can proceed. Lorentz's contributions to
this subject were, in Einstein's opinion, his great
achievement. His proof that essentially there are
not four fields but rather two is an achievement
of the greatest historical importance.

Professor Einstein told me that he felt that the
history of the development of ideas in science is
neglected. He was not interested in the history of
data — when, who did this, etc., — but in the

tracing of the evolution of ideas. "Most scientists
today do not seem to realize that the presenl
position of science can have no lasting signifi
cance." I asked him if it was not probable that
the next great advances in physics would be
farther in the future than most "planners" would
admit, and he laughed and said, "Yes, yes they
are all trying to get their results too cheap!"

Einstein then told me again how beautiful he
considered "Michelson's rotation of the earth
experiment." (Michelson-Gale experiment). He
considered this as one of the most beautiful of all
the experiments in physics and after the Michel-
son-Morley experiment, he considered it as
Michelson's greatest achievement. As Einstein
said, "Michelson could not stop and reverse the
rotation of the earth, so he accomplished the
same result by using a big path and a little path.
(Gestures). It is really not self-evident how this
could give the same result as stopping the earth."
(Here Einstein smiled with real joy.)

Einstein also mentioned the earth-tide ex-
periment 30 which he also liked very much. "This
experiment was out of his (Michelson's) line, but
an optical principle suggested itself to him and
made the measurement succeed."

I asked Einstein if he had any explanation for
the fact that Michelson first repeated the Fizeau
moving water experiment at Case before taking
up the repetition of his own Potsdam experiment.
Einstein said that it seemed very natural to him
that Michelson would take up the Fizeau experi-
ment and that this simply proved, "that the
whole problem was in Michelson's mind and that
he was thinking deeply on all aspects of it. The
Fizeau experiment and result was so funda-
mental that an improved repetition of it would in
any case be highly desirable." I asked Einstein if
he felt there had been any serious doubt at the
time about Fizeau's result, and he replied, "Oh,
every experiment should be repeated and refined
whenever possible." Several times he said, "I
really loved Michelson."

I told Einstein that in Michelson's lectures on
optics to his students at Case he had not men-
tioned the results of his own Potsdam experiment
or even described his own form of interferometer.
Einstein thought this was natural, as a teacher

30 A. A. Michelson and H. G. Gale, J. Geol. 27, 595 (1919).

R . S . SHANK LAND

56

should tell his students only the completely
established facts. He added that if he were to give
lectures on theoretical physics, he would omit all
reference to his own more speculative work and
would reserve this for listeners who were more of
the type of "connoisseur," and who would
realize that many of the points were still not
finally settled.

I asked Professor Einstein about the three
famous 1905 papers 31 and how they all appeared
to come at once. He told me that the work on
special relativity "had been his life for over seven
years and that this was the main thing." How-
ever, he quickly added that the photoelectric
effect (he could not for a moment recall the
English word) paper was also the result of five
years pondering and attempts to explain Planck's
quantum in more specific terms. He gave me the
distinct impression that the work on the Brown-
ian movement was a much easier job. "A simple
way to explain this came to me, and I sent it
off."* 2

I mentioned that the parts of the Michelson-
M or ley apparatus are lost and that even the
exact place where the experiment was performed
is not entirely certain. To this he smiled and
shrugged and reminded me that physicists do not
collect and preserve in the sense of old book
collectors but that the ideas are the things of
permanent value.

Einstein told me that Michelson did not like
the relativity theory. He told Einstein this and
he also heard it from others. Einstein laughed and
added, "You know we were very good friends!"
Michelson said to Einstein that he was a little
sorry that his own work had started this "mon-
ster." Einstein then went on to tell me how
natural this attitude would be in Michelson and
that it was due simply to the fact that Michel-
son's love was to experience phenomena directly
and that as a result he did not like abstractions.
I commented that in a certain sense this was
similar to Goethe's attitude toward color theory.
To this Einstein replied, "Oh Michelson's
attitude was not that extreme or he would not
have been a physicist!" He also added that for

'i A. Einstein, Ann. Physik 17, 132, 549, 891 (1905).

32 Of course Einstein worked on problems of the Brown-
ian Movement a great deal. See his collection of papers
edited by R. Fiirth (Methuen and Company, Ltd., London,
1926).

Goethe every observation of Nature was a deep
and direct personal psychological experience and
that he would not permit the abstractions of
science to interfere. Much of Goethe's description
of color is very useful, and up to the point where
he simply attacked Newton blindly, he made real
contributions to the subject of colors, especially
for art. 33

Einstein talked to me a little about quantum
theory and added, "Here I am a heretic you
know (laughed), but someday I believe my
views will be found true. God did not invent the
Science of Probability you know!" He spoke very
highly of Bohm's work but was sure it is wrong.
"He got his results too cheap." Einstein told me
that Bohm was not reappointed because he
refused to testify against other people. Einstein
spoke very bitterly about the "dirty work" of the
Rosenbergs' relative who saved his life with
theirs. About publicity Einstein told me that he
had been given a publicity value which he did not
earn. Since he had it he would use it if it would do
good; otherwise not. He looked mostly at me
during the conversation, but occasionally his
eyes looked far out into the autumn leaves. As he
thought his great eyebrows and the top of his
head would move, and then his eyes would
brighten again to tell me something more.

It was now time for me to leave, and I thanked
him and will treasure the memory of him sitting
with a blanket over his knees, his great deep
smile, his boyish laugh and the sincere friendli-
ness of that heart and mind.

He came to the door of his study as 1 left. He
shook my hand and smiled and thanked me for
coming. Miss Dukas was standing in the hall as
I came out. I hope I did not tire him.

V. 11 December 1954

Arrived in Princeton on the 10:45 train from
New York and called Einstein's secretary from
the Princeton Inn. She told me that Professor
Einstein wanted to see me but that the doctor
was there and would I be willing to come in a
half-hour. I, of course, agreed and arrived at 112
Mercer Street about 11:30. I left my coat and
briefcase in the lower hall and Miss Dukas led
me upstairs and to the back of the house into

33 J. W. von Goethe, Nachtrage zur Farbenlehre (1810).

CONVERSATIONS WITH EINSTEIN

57

Professor Einstein's study. He arose from his
chair, shook hands and greeted me in a very
friendly manner. He began our conversation by
telling me that he found our arguments convinc-
ing and "a very fine paper." 84 He then "told me a
story." At a meeting at the Institute for Ad-
vanced Study several years ago, they discussed
Miller's results and Einstein had commented,
"God is hard on us, but He is not malicious! 36
Surely there is an explanation for Miller's re-
sults." (Much laughter by Professor Einstein.)
Einstein told me again that he was sure we had
found this, and that everyone was pleased. I
mentioned that Professor Dyson had made a
valuable suggestion which we had used to
improve our correlations with temperature
conditions. Einstein asked me to tell him
about Dyson's suggestion, and I discussed the
AT=Av|f-r t -l, (*= 1,2,3,4). Einstein thought
this a good suggestion and asked how it worked
out. When I told him rather well in all but one
case he replied, "You would expect that!" I told
him that Professor Miller had given me his data
and that I was pleased that we could carry out
his wishes and look into it a little more. He again
told me that he thought we had settled the
problem at last. He then told me that he felt
making the apparatus large was a mistake. "You
make your troubles bigger and gain so little." He
also asked me why no one had used vacuum in
the light paths to get away from temperature
effects. I told him I did not know but that Joos 26
had gone pretty far and that by using helium,
Kennedy 36 had accomplished much the same
result.

When I began to tell him why I had felt it
necessary to get into the "frame of mind" that
suggested going to Mount Wilson, he empha-

34 This was the final draft of the paper subsequently
published by, R. S. Shankland, S. W. McCuskey, F. C.
Leone, and G. Kuerti, Revs. Modern Phys. 27, 167 (1955).

35 Over a fireplace in Princeton's Fine Hall are almost
these same words of Einstein : "Raffiniert ist der Herr Gott,
aber boshaft ist er nicfit."

36 R. J. Kennedy, Proc. Natl. Acad. Sci. U. S. 12, 621
(1926) ; Astrophys. J. 68, 361 (1928).

tically agreed. "You could not properly compre-
hend the work unless you did this." However, he
added that the idea that a bigger "aether wind"
would exist on a mountain had always been
impossible to bring into a picture with the facts
of astronomical aberration.

We then chatted briefly about Michelson, and
he again told me that he considered him a
"wonderful man." "Of course," Einstein added,
"He told me more than once that he did not like
the theories that had followed from his work!"
(Much laughter by Professor Einstein.)

We looked out of his windows to the bare
trees of the December land, and then I felt I had
stayed long enough. I asked him not to rise as I
took my leave, but of course he did. I paused to
look at the pictures on his study wall of Faraday
and Maxwell. He spoke highly of each and said
he especially liked the picture of Faraday. I told
him I had his latest book and had enjoyed read-
ing in it, especially the last tribute to Lorentz
(for his centenary). 37 He became most serious
and said, "People do not realize how great was
the influence of Lorentz on the development of
physics. We cannot imagine how it would have
gone had not Lorentz made so many great
contributions."

We shook hands, and I started down the hall,
and he followed, telling me (only now!) that he
was not too well and had a "strong anemia." At
the top of the stairs we again shook hands, and
he smiled with that deep and humble expression
with which he had first greeted me, gripped my
hand, then raised his hand in a sort of salute and
said, "Goodbye."

ACKNOWLEDGMENTS

I am greatly indebted to my colleagues,
Professors Sidney W. McCuskey, Leslie L. Foldy,
and Martin J. Klein for advice in the preparation
of this paper.

37 A. Einstein, Ideas and Opinions (Crown Publishing
Company, New York, 1954), pp. 70-76. See also G. L.
deHaas-Lorentz, H. A. Lorentz (North-Holland Publishing
Company, Amsterdam, 1957), pp. 5-9.

July 1973

Conversations with Albert Einstein. II

R. S. SHANKLAND
Department of Physics
Case Western Reserve University
Cleveland, Ohio 44^06

(Received 13 February 1973; revised 2 March 1973)

Professor Einstein's views on the experimental basis for
relativity theory and his attitude toward quantum me-
chanics continue to be of general interest. This paper is
based on notes on these subjects made by the writer after
each of five visits with Einstein at Princeton during
1950-1954 and not fully reported or discussed previously.

In 1963 I reported on five visits with Prof.
Einstein in Princeton during the period 1950-
1954. 1 These discussions were published almost
verbatim, with but little comment by me. They
have since been referred to in several articles on
the history of physics, so it now seems appropriate
to supplement the first publication by a more
complete discussion of certain statements made
to me by Prof. Einstein. I would like especially to
record my impressions of Einstein's views on the
role of the experiments of Michelson and Morley
and others in the development of the theory of
relativity and also to comment more fully on his
attitude on quantum mechanics.

THE MICHELSON-MORLEY EXPERIMENTS

Professor Einstein's statements on the Michel-
son- Morley experiment and its influence on his
work in the special theory of relativity were made
on several occasions and are not entirely con-
sistent; this is not too surprising in view of the
fifty year interval involved. As this experiment
was performed in Cleveland and had played a
central role in the contributions of H. A. Lorentz,

Henri Poincare, and others, it was only natural to
ask Einstein what relation it had had to his own
work. During our discussions he always expressed
the highest admiration for Lorentz ("the great
Lorentz," as he said several times) and for his
publications during the decade prior to 1905. It
did not occur to me to ask Prof. Einstein about
Poincare and his influence on his work, but I have
since learned from Miss Helen Dukas, Prof.
Einstein's secretary, that they had very little
correspondence. In the Einstein archives at
Princeton there is a letter of recommendation 2
which Poincare wrote for Einstein in 1911;
however, it does not specifically mention Einstein's
contributions to the special theory of relativity.
I have regretted that I did not ask Prof. Einstein
about Poincare for he would certainly have given
me detailed answers to any questions and made
clear the relationship of his own work to that of
Poincare, as he did with Lorentz. It is well
established that during Einstein's years in the
Swiss Patent Office at Berne (1902-1909) he was
the leader in an evening study group (including
Maurice Solovine and Conrad Habicht) called
"Olympia," which was active from 1902 through
1905. Books which they studied in detail included
Ernest Mach's Science of Mechanics, Dedekind's
work on Numbers, and Poincare's La Science et
L'HypotheseJ The latter work discusses the
Michelson-Morley experiment and includes Poin-
care's thoughts on the principle of relativity, both
for uniform motion and accelerated systems. It
thus seems clear that Einstein, who had already
published several original research papers in the
Annalen der Physik in the period 1900-1905, was
acquainted with some of Poincare's contributions
to the principle of relativity, as he was with the
writings of Lorentz. 3

Professor Einstein told me several times during
our talks in Princeton that he had learned of the
Michelson-Morley experiment through the writ-
ings of H. A. Lorentz. It was my understanding
during our talks that Prof. Einstein was well
aware of the null results of a wide range of both
first order (v/c) and second order (v/c) 2 aether-
drift experiments conducted throughout the 19th

AJP Volume 41 / 896

R. S. Shankland

century. This is clearly substantiated by the
following statement in his famous 1905 paper 4 :
. . the unsuccessful attempts to discover any
motion of the earth relative to the 'light medium,'
suggest that the phenomena of electrodynamics as
well as mechanics possess no properties correspond-
ing to the idea of absolute rest. They suggest
rather that as has already been shown to the first
order of small quantities, the same laws of electro-
dynamics and optics will be valid for all frames of
reference for which the equations of mechanics
hold good . . . ." The unsuccessful attempts clearly
refer to the (v/c) 2 experiments; among these, the
Micheison-Morley experiment was the most
definitive.

It is unlikely that he had studied the details of
the technique of the various experiments, but he
probably knew more about these than might be
assumed. I found his interest in and knowledge of
the essential features of the apparatus used by
Michelson and Morley, Fizeau, Zeeman, Sagnac,
Harress, Tomaschek, and Michelson and Gale
to be much more than I had anticipated would be
the case.

The several statements which Einstein made to
me in Princeton concerning the Micheison-Morley
experiment are not entirely consistent, as men-
tioned above and in my earlier publication. His
statements and attitudes towards the Micheison-
Morley experiment underwent a progressive
change during the course of our several conversa-
tions. I wrote down within a few minutes after
each meeting exactly what I recalled that he had
said. On 4 February 1950 he said, "... that he
had become aware of it through the writings of
H. A. Lorentz, but only after 1905 had it come to
his attention." But at a later meeting on 24
October, 1952 he said, "I am not sure when I first
heard of the Michelson experiment. I was not
conscious that it had influenced me directly during
the seven years that relativity had been my life.
I guess I just took it for granted that it was true."
However, in the years 1905-1909 (he told me)
he thought a great deal about Michelson's result
in his discussions with Lorentz and others, and
then he realised (so he told me) that he "had been
conscious of Michelson' s result before 1905 partly
through his reading of the papers of Lorentz and
more because he had simply assumed this result of
Michelson to be true." Since there are these

conflicting statements it may be of interest to
comment further on this situation.

When I first called on Professor Einstein in
Princeton on 4 February 1950, he was unac-
quainted with me and may possibly have wondered
if I had not come as the successor of Professor
Dayton C. Miller at Case to talk about Miller's
"aether drift" experiments at Mount Wilson.
These were certainly on my mind, but at that
first meeting my primary objective was to ask him
about the two Micheison-Morley experiments
performed at Cleveland in 1886 and 1887. But
before my views became clear to him, Prof.
Einstein volunteered a rather strong statement
that he had been more influenced by the Fizeau
experiment on the effect of moving water on the
speed of light, and by astronomical aberration,
especially Airy's observations with a water filled
telescope, than by the Micheison-Morley experi-
ment. This keen interest in the Fresnel-drag of
moving water had been shared by many workers
on the "aether problem," For example, at the
"Baltimore Lectures" of Lord Kelvin (then
Sir William Thomson) in 1884, both he and Lord
Rayleigh, who was present, urged Michelson and
Morley to repeat the Fizeau experiment as an
essential preliminary to their more famous
Micheison-Morley experiment. Their interest was
to clarify the effect of the postulated Stokes drag
of the aether by the earth and the resulting
decrease in the expected velocity of the aether
through the interferometer in the Micheison-
Morley experiment. However, the close relation
of the Fizeau experiment to the relativistic veloc-
ity addition theorem was the prime reason for
Einstein's interest in this subject.

As clearly reported by Max Wertheimer, 6 who
in 1916 discussed with Einstein the development
of his ideas in special relativity in great detail,
it is evident that the importance of the Micheison-
Morley experiment for Einstein was that it gave
positive confirmation to his belief that the speed
of light is invariant in all inertial frames, inde-
pendent of the motion of source, apparatus, or
observer. Such invariance in c was necessary for
his interpretation of Maxwell's equations and for
his derivation of the Lorentz transformation, as
well as for his conviction that the "local time,"
first introduced by Lorentz, is indeed the only
true time for the description of physical phenom-

896 I July 1973

Conversations with Albert Einstein. II

ena. Professor Einstein's statement to me was
that "at last it came to me that [absolute] time
was suspect," and that the new absolute for
physics must be the speed of light in. vacuum,
rather than space and time. These conclusions,
and also the relativity principle for uniform
motion to the greater sensitivity (v/c) 2 than had
been shown by any previous "aether drift"
experiments, were strongly supported by the
Michelson-Morley experiment, which showed no
change in the speed of light with respect to direc-
tion and revealed no absolute motion of the inter-
ferometer through space. It is of interest to note
that even in 1950 Einstein was concerned with
the possible periodic changes in c which had
recently been reported, and asked if I thought the
effects were real. When I told him I believed they
were spurious, he seemed obviously pleased. The
fact that he was so interested in these measure-
ments in 1950 makes it very difficult to believe that
he was unaware of any important work bearing on
the problem in the years before 1905.

When Prof. Einstein realized that I had not
come as an advocate for Miller's results his
attitude became less formal and our conversations
were much more relaxed. Indeed, it was largely
his encouragement and advice that made me feel
it would be desirable for us to make the study
which finally revealed the cause of Miller's
periodic fringe shifts. I should add that in doing
this we were also carrying out the wishes of Prof.
Miller who died without having resolved the
question and who had suggested that we restudy
his data if it were thought desirable. Professor
Einstein's statements to me about Prof. Miller
and his experiments were uniformly respectful,
though it was clear that he felt sure they were in
error. He also told me that II. A. Lorentz had
tried without success to explain Miller's results.

In this connection it is of interest to note that
in 1921 when Miller first announced the periodic
fringe shifts in his interferometer experiments on
Mount Wilson, Einstein was lecturing on relativity
at Princeton. He told me that it was Miller's
work that had prompted his remark now inscribed
in the stone fireplace at Fine Library, "Raffiniert
ist der Herr Gott, aber boshaft ist er nicht." When
he learned of Miller's result he travelled to Cleve-
land to see him and they had a long discussion
about the Mount Wilson experiments. Professor

Einstein told me that at that time he did not feel
sure of a single English word, 1 but Prof. Miller
could speak German rather fluently, for
youth in Berea, Ohio, his playmates were the
children of German Methodist ministers teaching
at Wallace College (now a part of Baldwin-
Wallace College) . The writer has a sketch made
by Prof. Einstein during this visit on 25 April 1921
indicating how the postulated Stokes drag of the
"aether" by the earth would become progressively
smaller with elevation above sea level so that on
Mount Wilson the expected fringe shifts in the
interferometer should be considerably greater
than in the basement laboratory at Cleveland.
Of special interest on the sheet with Einstein's
sketch is the word "Fizeau" written by Miller,
probably because Einstein had discussed the
Fizeau experiment and its greatly improved
repetition by Michelson and Morley at Case in
1886. This notation again emphasizes the im-
portance that Einstein attached to this experiment
and proves that even in 1921 he considered the
phenomenon of the effect of moving water on the
speed of light as a major observational fact for his
work on special relativity. By assuming an
invariant upper limit for the speed of light in
vacuum, the derivation of the relativistic velocity
addition theorem, which is closely related to the
Fresnel drag, follows directly. The word "Fizeau"
written on Einstein's sketch may also indicate
that as early as 1921 when Miller's positive result
seemed definite, Einstein may have been looking
elsewhere than to the Michelson-Morley experi-
ment for experimental support for the postulates
of relativity. It also could mean, as he told me in
1952, 1 that he had suggested to Miller that the
Fresnel drag by the Mount Wilson interferometer
itself would greatly reduce the expected fringe
displacements.

When we 6 finally found the cause of Miller's
periodic fringe shifts to be temperature gradients
across the interferometer, Einstein was genuinely
pleased and, in fact, wrote me a fine letter on the
subject. I only learned after his death that he
had written to Ehrenfest after Miller's 1921
announcement, suggesting that temperature effects
might be responsible for the results; it is curious
that he never mentioned this to me. Whether he
had forgotten about it or whether he wanted us to
find the solution in our own way, I cannot say;

AJP Volume 41 / 897

B. S. Shankland

but of his genuine interest in finding the correct
answer there can be no doubt.

It is important to note that in talking with
M. Wertheimer in 1916, Einstein's references to
experiments were amost exclusively to the better
known Michelson-Morley experiment. 5 This was
five years before Miller's first experiments. This
writer finds the account of Wertheimer entirely
consistent with his own notes and recollections of
Einstein's attitude in 1952 toward the Michelson-
Morley experiment.

The writer is convinced on the basis of his dis-
cussion with Prof. Einstein that he certainly knew
about the Michelson-Morley result before 1905
and also was conversant with a wide range of both
the experimental and theoretical work in the
physics literature bearing on the "aether problem"
before 1905. However, the exact relation which any
specific experiment or the theoretical work of
other physicists bore to his own creations is not
possible to determine with certainty; even Ein-
stein himself was not sure. But to believe that he
could be unaware of important experiments or
theoretical developments in the decade before
1905 is entirely inconsistent with his profound
understanding of the development of physics, as
was clearly evident even in his later years.

It should be noted that in 1905 it was not the
practice to give specific references in published
papers as it is today. Many important papers gave
no references whatever, so the fact that Einstein's
1905 paper (which has no references) makes no
explicit mention of the Michelson-Morley experi-
ment is not in the least unusual. To what degree
and at what stage of his activities he was directly
influenced by the work of others, it is now im-
possible to determine. But I became convinced
that his interest in the Michelson-Morley experi-
ments (both those of 1886 and 1887) had existed
before 1905.

EINSTEIN'S ATTITUDE TOWARD
QUANTUM MECHANICS

One of the great puzzles in physics was the
attitude of Prof. Einstein toward the new quantum
mechanics developed during the years after 1925.
His position was strange not only because of his
great contributions to physics in general, but

especially so in view of his leading role in the
development of the old quantum theory from 1905
to 1925, when his photoelectric theory, photon
hypothesis, the concept of induced transitions,
the first quantum theory of the specific heat of
solids, and the Bose-Einstein condensation and
statistics were all major achievements leading to
the new quantum mechanics. However, when it
became clear that the new theory had essential
statistical elements, then Einstein turned com-
pletely against it and for the remainder of his life
was an active opponent.

There is, of course, no way to determine with
certainty why this change of heart took place.
But we can recall that during the years 1919-
1925 following Eddington's successful eclipse
confirmation of the deflection of starlight by the
sun, Einstein suddenly became a world figure
and began lecturing and working for political
causes that required a significant fraction of his
time and energy. It was in this period that the
new quantum mechanics was developed by Bohr,
Heisenberg, Pauli, Dirac, Schrodinger, Born, and
others, without Einstein having a major role.
Nevertheless, during this period he had main-
tained an active interest. He was one of the first
to hail the discovery of the Compton effect; here
his opposition to probability theories first strongly
appeared when he disavowed the statistical theory
of Bohr, Kramers, and Slater 7 as a valid descrip-
tion of this scattering phenomenon. Even when
the Compton effect was shown to give a clear
example of the Heisenberg uncertainty principle,
Einstein was not won over, although enthusiastic
for its support of the photon theory of radiation.
But even his earlier use of statistical methods to
predict the existence of photons traveling with
energy hv did not affect his attitude toward the
new quantum mechanics and especially its
statistical features toward which he remained
consistently hostile.

This greatly influenced his relations with Niels
Bohr and the "Copenhagen School." Although
Bohr and Einstein were uniformly courteous at
their meetings and in correspondence, they both
at times became highly emotional in their views on
the basic correctness and completeness of the
quantum-mechanical description of nature. Ein-
stein made statements to the writer which were
very strong in his criticisms of Bohr, Heisenberg,

898 I July 1973

Conversations with Albert Eimtein-II

Dirac, Oppenheimer, and others who shared their
views. Even Dime's relativistic development of
quantum theory failed to alter Einstein's opinion
in statements he made to me. We also know from
friends who studied in Copenhagen that Prof.
Bohr, in spite of his extremely polite and detailed
refutations of the various quantum paradoxes
proposed by Einstein, was often very emotional
on this subject. Bohr even became highly critical
of Bohm's work on "hidden variables," and
considered his attempt for a deterministic picture
to be philosophically a step backward.

Recent experiments at Berkeley by E. D.
Commins and his research students 8 have shown
that the correlation in linear polarization between
two photons emitted in an atomic cascade is in
complete agreement with quantum mechanics
and in direct conflict with all "hidden variable"
theories which have been proposed to give an
underlying deterministic structure such as Einstein
held to be essential for a complete theory. 9

The discussions between Einstein and Bohr at
Solvay Conferences and elsewhere of the paradoxes
by which Einstein hoped to reveal basic defects
in quantum mechanics are highly interesting and
clarify many subtle points. But it is clearly
evident that time and again Bohr successfully
defended the quantum mechanical description of
nature against Einstein's criticisms. One of the
most dramatic of these exchanges is that where
Bohr used the general theory of relativity to
explain a paradox proposed by Einstein at their
last Solvay Conference meeting in 1930. 10

The question has often been asked : How would
Einstein's attitude toward the unified field theory
have been affected by the problem of including the
weak and strong nuclear interactions; and especi-
ally how would he have reacted to the failure of
parity and other invariance principles. He, of
course, did not discuss this, but it seems to me
that since his basic philosophy was always directed
toward the unification of physics, he would have
maintained his faith that an all embracing unified
field theory would ultimately be found. He did
express the strong conviction to me that the present
lack of success is due to approximation methods
that fail to reveal true insights into phenomena,
that only when great advances in mathematics
make rigorous solutions possible will significant
progress be made in theoretical physics, and that

"the final solution must start with general
relativity."

It was clear that Prof. Einstein (in his state-
ments to me) regarded quantum mechanics as a
valid computational tool, but he could never
accept the philosophical implications of its
statistical basis or believe it was a complete
description of nature. He felt sure that eventually
a foundation would be found for quantum
mechanics that would restore causality and elim-
inate the uncertainty principle and the statisti-
cal description and provide a complete theory.
This viewpoint emphasizes the fact that Einstein
was at heart a classical physicist. His relativity
theories were the capstone of the classical physics
of the 19th century, and the complete break with
this structure made by the new quantum me-
chanics appeared to be too much for Einstein to
accept.

Today, the majority of physicists have not been
greatly influenced by Einstein's attitude toward
the new quantum mechanics, but there must
nevertheless be a lingering question that some
elements of his position may yet prevail, eventu-
ally to influence future developments. However,
certain points are clear. In the development of
physics which led to the theory of relativity, there
had gradually accumulated basic paradoxes and
conflicts between theory and experiment that
were only finally resolved by the theory of rela-
tivity. These included the null result of the
Michelson-Morley experiment, the Fizeau and
Michelson and Morley measurements of the
Fresnel drag on light in moving water, an ap-
parent favored inertial frame for Maxwell's
equations, certain asymmetries in electrodynamics
that did not seem inherent in the phenomena, etc.
These finally pointed the way to new concepts of
space and time in physics, leading at first to the
special theory of relativity and then to the general
theory of relativity and gravitation.

Other paradoxes in physics were finally resolved
only by the development of the new quantum
mechanics. Chief among these were the photo-
electric effect, the Compton effect, phenomena
that required wave or particle properties for radia-
tion, electron diffraction and the wave nature of
matter, the anomalous Zeeman effect, the Stern-
Gerlach experiment, the existence of discrete
energy states and transitions in atomic and

AJP Volume 41 / 899

R. S. Shankland

molecular systems, and others. These paradoxes
and contradictions were only removed with the
advent of quantum mechanics.

Today the situation is entirely different. At
present there seem to be no basic paradoxes or
conflicts between theory and experiment of the
nature that suggest that quantum mechanics is
wrong. To be sure, there are great difficulties, but
these can be viewed as largely computational in
nature and not related to the basic validity of
quantum mechanics itself. The development of
more powerful forms of mathematics may enable
many of these problems ultimately to be solved.
The present difficulties in the application of
quantum mechanics chiefly involve such factors
as the lack of detailed and certain knowledge of
the nuclear force and things of that nature and
are not inherent in quantum mechanics. Even the
failure of invariance principles, such as "C,"
"P," and £i CP" in no way affect the validity of
quantum mechanics but merely affect the forms
of the Hamiltonian that can be employed in the
solution of specific problems.

Einstein's attitude toward quantum mechanics
was well known but for the record we give some
of the statements he made to me during my visits
in Princeton. These are listed here out of context
but they serve to show the depth of feeling for
the convictions he held. In making these state-
ments to me, Prof. Einstein often exhibited great
emotion and there was certainly no question that
his opposition to quantum mechanics was very
intense.

Atomistic phenomena must fit into a unified
field theory.

You know I am in disagreement with most
of my colleagues on the quantum theory.

They are not facing the facts!

They have abandoned reason! [with great
emphasis 0

Quantum mechanical physics avoids reality
and reason!

Bohr's thinking is clear but when he
begins to write he becomes very obscure
and he thinks of himself as a prophet.

Bohr always speaks ex cathedra.

On Quantum Theory I am in the opposition.

The \p functions do not represent reality.

Quantum mechanics is a brilliant shortcut
which successfully avoided many of the
difficulties and the hard work which the final
correct theory must face and solve.

Bohm got his results too cheap.

I have talked very little with Oppenheimer
about it.

The final correct solution must start with
general relativity.

Here in quantum mechanics I am a heretic,
you know [laughed] but someday I believe
my views will be found true. God did not
invent the science of probability, you know.

In closing this account, I would like to express
my admiration for Professor Einstein in words of
one of the greatest poets 11 :

And now his work is done. It will endure,
We trust, beyond Jove's anger, fire and
sword,

Beyond Time's hunger. It will be borne
Above the stars, and shall be living, always.

* This account was given during 1972-1973 for physics
colloquia at Purdue University; Wilmington, Delaware
R.E.S.A.; Rensselaer Polytechnic Institute; and Indiana
University. It is a pleasure to acknowledge my thanks for
the helpful discussions at these meetings, and also with
my colleagues at Case Western Reserve University and
Prof. Luis W. Alvarez.

1 R. S. Shankland, Amer. J. of Phys. 31, 47 (1963).

2 See Albert Einstein by Carl Seelig for Poincare's letter
in French on p. 163 in the original 1954 edition; in the
English edition, Savill translation, pp 134-135 (Staples,
London, 1959). See also p. 57 of the English edition for
"Olympia" reading list.

* For an excellent, balanced, and detailed discussion of
the contributions of Lorentz, Poincar£, Einstein, and
Minkowski to the development of the special theory of
relativity, see G. H. Keswani, British J. Phil. Sci. 15, 286
(1965) ; 16, 19, 273 (1965-66). See also, "Poincare's Rendi-
conti Paper on Relativity" by H. M. Schwartz, Amer, J.
Phys. 39, 1287 (1971); 40, 862 (1972); 40, 1282 (1972).

* A. Einstein, Ann. der Physik 17, 891 (1905) , Italics are
mine.

900 / July 197S

Conversations with Albert Einstein- 1 1

6 M. Wertheimer, Productive Thinking (Harpers, New
York, 1945, 1959), Chap. 7 on "Einstein: The Thinking
that Led to the Theory of Relativity."

6 R. S. Shankland, S. W. McCuskey, F. C. Leone, and
G. Kuerti, Rev. Mod. Phys. 27, 167 (1955).

* N. Bohr, IT. A. Kramers, and J. C. Slater, Phil. Mag.
47,785 (1924).

8 C. A. Kocher and E. D. Commins, Phys, Rev. Let-

ters, 18, 575 (1967) ; S. J. Freedman and J. F. Clauser,
Phys. Rev. Letters 28, 938 (1972).

3 A. Einstein, B. Podolsky, and N. Rosen, Phys. Rev.
47, 777 (1935).

10 Niels Bohr in Albert Einstein, Philosopher-Scientist,
edited by P. A. Schlipp, (Library of Living Philosophers,
New York. 1949), pp. 224-228.

11 Ovid, Metamorphoses XV, Epilogue.

LETTER TO THE EDITOR

Comment on "Conversations with Albert
Einstein. II"

R. S. Shankland

Department of Physics

Case Western Reserve University

Cleveland, Ohio 44106

(Received 20 May 1974; revised 7 August 1974)

Several readers of the article on "Conversations with
Albert Einstein. II," published in the July 1973 issue of
this Journal, 1 have expressed interest in the work of Poin-
care, which was studied by Einstein and the Olympia
Club in Bern prior to 1905. This letter gives the specific
reference alluded to on p. 895 of Ref. 1 .

The following statement appears on p. 201 of the 1903
edition of Poincare's book La Science et VHypothese 2
(the italics are mine).

Et maintenant il faut qu'on me permette une di-
gression; je dots expliquer, en effet, pourquoi je ne
crois pas, malgre Lorentz, que des observations
plus precises puissent jamais mettre en evidence au-
tre chose que les deplacements relatifs des corps
materiels. On a fait des experiences qui auraient du
deceler les termes du premier ordre; les resultats ont
ete negatifs; cela pouvait-il etre par hasard? Per-
sonne ne l'a admis; on a cherche une explication
generate, et Lorentz l'a trouvee; il a montre que les
termes du premier ordre devaient se detruire, mais
il n'en etait pas de meme de ceux du second. Alors
on a fait des experiences plus precises; elles ont
aussi ete negatives 3 ; ce ne pouvait non plus etre
1 'effet du hasard; il fallait une explication; on l'a
trouvee; on en trouve toujours; les hypotheses, e'est
le fonds qui manque le moins. 4

This statement clearly distinguishes between the vie and
v 2 /c 2 "aether drift" experiments that were so much in the
scientific literature of that day. While there is no explicit
mention of the Michelson-Morley experiment by name, it

seems to me that the words in italics (mine) clearly refer
to their result. It was not then the usual practice to burden
research papers with footnotes and references to well-
known results, and the Michelson (1881) and the
Michelson-Morley (1887) experiments had been discussed
repeatedly in the literature from 1881 on into the 20th
century. Often their result was referred to in a very gen-
eral way as in Poincare's book, although in his 5 June
1905 paper 5 Poincare was explicit about Michelson (but
not Morley).

Einstein, in his famous 1905 6 paper (which has no
specific references), refers to both vie and v 2 /c z experi-
ments in much the same way as Poincare had done. Ein-
stein's words are as follows (the italics, again, are mine).

Beispiele ahnlicher Art, sowie die misslungenen
Versuche, eine Bewegung der Erde relativ zum
"Lichtmedium" zu Konstatieren, fiihren zu der
Vermutung, dass dem Begriffe der absoluten Ruhe
nicht nur in der Mechanik sondem auch in den
Electrodynamik keine Eigenschaften der
Erscheinungen entsprechen, sondem dass vielmehr
fur alle Koordinaten systeme, fur welche die
mechanischen Gleichungen gelten, auch die
gleichen elektrodynamischen und optishen Gesetze
gelten, wie dies fur die Grossen erster Ordnung be-
reits erwiesen ist.

J R. S. Shankland, Am. J. Phys. 41, 895 (1973).

2 H. Poincare, La Science et VHypothese (Flammarion, Paris, 1903).

3 This clearly refers to the v 2 /c 2 experiments of Michelson and Morley

and also, possibly, to those of Trouton and Noble [Philos. Trans. R.

Soc. Lond. 202, 165 (1903)] and of Lord Rayleigh [Philos. Mag.

4, 215 (1902)].

4 One detects in these last words Poincare's coolness to the ad hoc na-
ture of the original Fitzgerald-Lorentz contraction hypothesis. This
was in 1903 before its later formulation by Lorentz in 1904.

& H. Poincare, C. R. Acad. Sci. (Paris) 140, 1504 (1905). In this paper
Poincare first named the Lorentz transformation and proved that it is
a mathematical group and then extended the 1904 theory of Lorentz
to obtain the transformations for electric charge and electric current
density.

"A. Einstein, Ann. Phys. (Leipz.) 17, 891 (1905).